1. Field of the Invention
This invention relates to a composition comprising an aqueous cellulosic furnish, cationic polymer and a modified lignin and methods using the composition for making paper or paperboard having improved properties in the areas of drainage, retention and formation.
2. Brief Description of the Background Art
In the production of paper or paperboard from a dilute aqueous cellulosic furnish improvements in retention and drainage and in the formation properties of the final paper or paperboard sheet are particularly desirable. It is well known by those skilled in the art that these parameters are frequently in conflict with each other. For example, if the cellulosic fibers of the aqueous cellulosic furnish are flocculated effectively to larger flocs, retention of, for example, fiber fines and filler is generally good and can result in a porous structure yielding generally good drainage; however, formation is poor. In this light, conventional practice has resulted in those skilled in the art selecting one or more additives to improve the production of paper or paperboard according to the parameters that are most important to achieve. Alternatively, if the cellulosic fibers are flocculated to a lesser degree, drainage and retention are less satisfactory; however, formation is improved. Further, drainage and retention are often in conflict with each other when, for example, increased production of paper or paperboard is desired over the need for retention of, such as for example, fillers and the like.
Retention is believed to be a function of different mechanisms such as filtration by mechanical entrainment, electrostatic attraction and bridging between aqueous cellulosic fibers and filler. Because both cellulose and many common fillers are electronegative, they are mutually repellant and, in the absence of a retention aid, the only factor tending to enhance retention is mechanical entrainment.
Drainage relates to the rate at which free water is released from a sheet as it is being formed. Thus, it will be appreciated that drainage aids improve the overall efficiency of dewatering in the production of paper or paperboard.
Formation relates to the formation of the paper or paperboard sheet produced from the papermaking process. Formation is generally evaluated by the variance in light transmission within a paper sheet. A high variance is indicative of poor formation. It is generally well known by those skilled in the art that as the retention level increases, the level of formation generally decreases from good formation to poor formation.
A variety of compositions and processes have been proposed to improve retention, drainage, or formation to improve the papermaking process.
U.S. Pat. No. 4,913,775 (Langley et al) discloses a process of making paper or paper board comprising passing an aqueous cellulosic suspension through one or more shear stages, draining the suspension to form a sheet and drying the sheet wherein an improved combination of retention, drainage, drying and formation is achieved by adding to the suspension an excess of high molecular weight linear synthetic cationic polymer before shearing the suspension and adding bentonite after shearing.
U.S. Pat. No. 4,643,801 (Johnson) discloses a paper making process in which paper making stock containing a sufficient amount of cellulosic pulp is formed into a sheet and dried and to which is added prior to formation of the sheet a coacervate binder comprising a cationic starch, a high molecular weight anionic polymer and a dispersed silica.
U.S. Pat. No. 4,388,150 (Sunden et al) discloses a paper making process and an improved cellulosic paper product. This patent states that a paper making process is provided in which an aqueous papermaking stock containing a sufficient amount of cellulosic pulp is formed and dried, wherein the improvement comprises providing in the stock prior to the formation of the sheet a binder comprising colloidal silica acid having an average particle size less than 20 nanometers and cationic starch. This patent states that the cationic starch and the colloidal silica acid are admixed with each other in the presence of cellulosic fiber to form a complex of cationic starch and colloidal silica acid which serves as a binder for the cellulosic fibers.
U.S. Pat. No. 5,098,520 (Begala) discloses a process in which paper or paperboard is made and wherein drainage and/or retention is improved including forming an aqueous cellulosic papermaking slurry that is subject to one or more shear stages, adding sequentially to the slurry a mineral filler, a high molecular weight cationic polymer that is a (meth)acrylamide polymer, and a medium molecular weight anionic polymer.
U.S. Pat. No. 5,185,062 (Begala) discloses a process in which paper or paperboard is made and wherein drainage and/or retention is improved including forming an aqueous cellulosic papermaking slurry that is subject to one or more shear stages, adding sequentially to the slurry a (meth)acrylamide polymer and a medium molecular weight anionic polymer having at least 20 mole percent ionizable mer units including at least 10 mole percent sulfonate-containing mer units.
U.S. Pat. No. 4,313,790 (Pelton et al) discloses a papermaking process for simultaneously increasing the retention of fines, fillers and pigments and decreasing the deposition of pitch on the papermaking apparatus comprising adding to an aqueous wood slurry a poly(oxyethylene) and a kraft lignin product.
U.S. Pat. No. 4,347,100 (Brucato) discloses a method of producing paper having improved bursting strength from mechanical or thermomechanical pulp comprising defibering wet wood by mechanical attrition to form mechanical or thermomechanical pulp, processing the pulp to form a furnish, incorporating into the pulp at an elevated temperature and pressure an anionic organic polyelectrolyte or polymer to improve bursting strength, and adding to the furnish a cationic organic polyelectrolyte or polymer. The patent states that the anionic organic polyelectrolyte or polymer causes dispersion of lignin and retards deposition of lignin to improve the bursting strength. This patent discloses that the anionic polyelectrolyte or polymer must be incorporated into the pulp by cooking at elevated temperature and pressure before or during the refining or defibering stage to achieve the desired end result of paper having improved bursting strength. This patent states that the anionic organic polyelectrolyte or polymer is a polymeric sulfonate.
U.S. Pat. No. 4,606,790 (Youngs et al) discloses a method of preparing an electrically conductive multi-ply structure for intercepting and dissipating electrostatic charges and discharges comprising forming in a mixing vessel an aqueous slurry consisting essentially of a fibrous material, particles of an inorganic electrically conductive substance and an electroconductive polymer dispersant, dispersing the particles in the mixing vessel in the presence of the fibrous material and the polymer dispersant, forming a plurality of separate aqueous slurries consisting essentially of a non-conductive fibrous material, transporting the slurry containing the particles of the conductive substance from the mixing vessel to a paper forming machine, and adding a retention aid polymer to the slurry. This patent states that the electroconductive polymer dispersant is a cationic amine-substituted polymethacrylate or an anionic alkali metal polyacrylate or lignosulfonate.
U.S. Pat. No. 4,145,246 (Goheen et al) discloses a linerboard composition and a process for producing the linerboard composition having a percent mullen of at least 80%, including a replacement quantity of sulfite-modified thermomechanical pulp. This patent states that the process for producing a linerboard composition comprises imparting mechanical attrition forces to undefibered lignocellulose which has been subjected to elevated temperature and pressure, adding a sulfite chemical to the lignocellulose prior to, during, or subsequent to the initial mechanical attrition, subjecting the sulfite-treated lignocellulose to a second mechanical attrition step, forming an aqueous linerboard furnish including at least 25% by weight of the sulfite-modified thermomechanical pulp, depositing the furnish on a foraminous surface to produce a wet linerboard web, and drying the linerboard web.
U.S. Pat. No. 3,180,787 (Adams) discloses a method for increasing the flexural strength of paper comprising adding a water soluble lignosulfonate salt to a water slurry of cellulose pulp, adding a polyethylene polyamine thereby precipitating insoluble polyethylene polyamine lignosulfonate, and forming the pulp fibers with adhered insoluble precipitate into a continuous paper web.
U.S. Pat. No. 4,772,332 (Nemeh et al) discloses a heat stabilized dispersed slurry of particles of chemically bulked hydrous kaolin clay pigment for use in coating or filling paper and method for preparing same. The patent states that the process comprises preparing a fluid aqueous suspension of kaolin clay, adding thereto a cationic polyelectrolyte for flocculating the clay suspension, filtering the suspension, washing the filtered clay, adding to the filtered clay a dispersant that is a combination of a polyacrylate salt, an anionic water soluble lignosulfonate and a water-soluble naphthalene sulfonate formaldehyde complex to provide a fluid suspension of bulked clay free from a phosphate dispersant.
U.S. Pat. No. 3,985,937 (Fife) discloses a corrugating medium laminating adhesive comprising a polymer latex emulsion adhesive containing polyvinyl acetate homopolymers and styrenebutadiene polymers admixed in water with a clay, a paraffin wax, a polyalkylene glycol wetting agent and a lignosulfonate dispersant.
U.S. Pat. No. 3,849,184 (Roberts) discloses a coated paperboard containing paperboard consisting of at least one ply consisting essentially of cellulosic fibrous materials, and a coating on at least one surface thereof comprising a water soluble lignosulfonate salt and a non-reactive hydrophobic waxy material.
U.S. Pat. No. 3,758,377 (Fife) discloses a process for the preparation of a paper sheet by treating the cellulosic fibers in an aqueous slurry with a mixture of a lignosulfonate and an isoprene resin stabilized with an urea-formaldehyde resin.
TAPPI, Papermakers Conference Proceedings, Book 1, pp. 115-186, (Atlanta, Georgia--Apr. 18-21, 1993) discloses microparticle systems such as for example, a system having a cationic starch or cationic polyacrylamide or anionic polymers and an anionic silica colloid or bentonite or alumina sol for improving dewatering, retention, formation and dry strength.
TAPPI, The Journal Of The Technical Association Of The Pulp And Paper Industry, Vol. 63, No. 6, pp. 63-66 (June, 1980) authorized by C. H. Tay, discloses that water soluble substances such as lignosulfonate originating from wood constituents deactivate cationic polyelectrolytes used for filler retention.
Colloids And Surfaces, Vol. 64, pp. 223-234 (1992), co-authored by P. Li and R. Pelton, discloses that cationic poly (diallyldimethyl ammonium chloride) increased the efficiency of the displacement washing of aqueous kraft lignin from a bed of glass beads. This publication states that improved washing results when the poly (diallyldimethyl ammonium chloride) concentration is high enough to form an insoluble complex with lignin.
TAPPI, Contaminant Problems And Strategies In Wastepaper Recycling, Seminar Notes (Madison, Wis.) pp. 91-96 (Apr. 24-26, 1989), authored by T. H. Wegner, discloses that pulping liquors, such as kraft lignin and saponified extractives, used in papermaking are a major source of white water contaminants and adversely affect the performance of a cationic polyacrylamide used as a drainage aid. More specifically, this publication states that kraft lignin completely negated the effectiveness of polyacrylamide as a drainage aid, and that fines retention was also adversely affected.
EUCEPA/ATICELCA, Devt. & Trends in Sci. & Technol. of Pulp & Pmkg., Vol. 2, Paper No. 31, pp. 1-22 (Oct. 6-10, 1986), co-authored by D. Ahrabi, L. Odberg and G. Strom, discloses that in closed white water systems anionic polymers such as, for example, lignin and lignosulfonate, interfere strongly with cationic polymers that are used to improve retention and drainage on the paper machine.
It will be appreciated by those skilled in the art that the above mentioned background technical publications teach against the addition of lignin or modified lignin to paper furnishes having a cationic component. Therefore, it will be understood by those skilled in the art that applicants have discovered unexpectedly that the composition and process of the instant invention comprising adding a modified lignin to an aqueous cellulosic furnish having a high molecular weight cationic polymer component results in producing paper or paperboard having improved drainage, retention and formation properties that are superior to results of others previously achieved.
In spite of this background material, there remains a very real and substantial need for a composition and process for making improved paper or paperboard in the areas of drainage, retention, or formation, and combinations thereof.